1. Technical Field
The present invention relates generally to an improved image display system in which electromagnetic energy beams (e.g. collimated laser beams) are steered reflected within a or substantially planar structure in such a way which minimizes transmission intensity losses and the required number of energizing (e.g. laser beam) sources therewith. Also, the present invention relates to a novel method of fabricating such improved image display systems and devices in an inexpensive and mass-production manner.
2. Brief Description of the Prior Art
The need to produce images for visual display is widespread in our society. For decades, cathode ray tubes (CRT) have been used to scan electron (i.e. cathode ray) beams across phosphor display screens in order to form images in accordance with video signals. By virtue of physical necessity, such electron beams have been deflected within CRTs using magnetic and/or electric force fields which vary over time in accordance with video signals representative of images being sequentially displayed.
As an alternative to CRT display devices, it is possible to form images on a display surface by scanning a laser beam, rather than an electron beam, through a volume of space across a display surface. This approach is similar to that employed during conventional laser light shows, except that during a laser light show the display surface is typically a ceiling surface or atmospheric vapor. Scanning a laser beam across such a display surface may be accomplished using a variety of electro mechanical or electro-acoustic scanning technologies, numerous examples of which are described in great detail in “Laser Scanning Notebook” by Leo Beiser, published November 1992 by SPIE Optical Engineering Press, Bellingham, Wash., USA. However, like CRT display systems, conventional laser scanning display systems cannot be made physically compact nor can they avoid the use of galvanometric and electro-acoustic scanning apparatus. Such image display techniques suffer from a number of shortcomings and drawbacks. In particular, display structures embodying these techniques require a large volume of space due to the small angle through which the light beam can be deflected. Thus, if it is desired to scan a length B, the deflection arrangement must be positioned at a distance, A, providing an A/B ratio larger than 1, and therefore making it difficult, if not impossible to construct a flat-type display panel structure for color image display.
During the past few decades, a need has arisen for image display devices having both flat panel surface characteristics and thin depth dimensions. Numerous image display systems having such characteristics have been developed. In general, such systems have pixelated display surfaces which produce images composed of light rays emanating from discrete pixel elements activated in accordance with video signals. An electrical voltage is derived from the video signal for each pixel along the display surface, and the derived voltage is used to change either the optical or electrical properties of the associated pixel. In the case of LCD panels, such changes in optical properties of the pixels permit selective passage of light produced from behind the display surface. In the case of plasma display panels, changes in the electrical properties of encased plasma gases result in emission of light from activated pixels.
While these prior art display technologies have made it possible to make flat display devices with very thin depth dimensions and thus overcome the principal drawbacks associated with CRT display devices, prior art flat panel device technology has nevertheless suffered from some very significant shortcomings and drawbacks. In particular, it is presently impossible to make large-area flat panel display panels using current LCD technology. In addition, conventional flat panel display panels are very inefficient in terms of energy usage. Consequently, the uses to which conventional flat panel display technologies can be put have been necessarily limited.
In International PCT Publication Number WO 95/24671, based on the teachings of U.S. Pat. No. 5,459,591 to S. M. Faris, which is incorporated herein by reference in its entirety, Applicants addressed the above-described problems associated with prior art flat-panel display technology. This was done by teaching how to make large planar display structures comprising a plurality of imaging cells arranged in the form of an array, wherein each imaging cell incorporates a solid-state cholesteric liquid crystal (CLC) element, an electronically controlled, variable half-wave retarder and a source of circularly polarized light. The CLC element is disposed to an angle (45.degree.) relative to the path along which light from the source is projected and is designed to reflect, at a given wavelength, one circular polarization of light and transmit the other. Using this characteristic, light of one polarization state or the other is presented to the variable retarder and depending on whether or not it is actuated, light is either diverted into another orthogonal path or remains in the original path. When another similar imaging cell is disposed in the orthogonal path, fight incident on that cell can also be diverted into yet another path or transmitted along the orthogonal path under control of a half-wave retarders associated with said another imaging cells. By selectively activating half-wave retarders associated with each of the cells, monochromatic or polychromatic light from a single source or multiple sources may be steered to a selected cell and reflected from its associated CLC element or elements. Utilizing successive cells in the array, and causing reflection of a modulated beam or beams, produces an image display frame akin to that produced by conventional television sets and viewable as an integrated picture. When successive image display frames are produced, moving images are displayed from the planar display structure.
While Applicants' prior art image display system addresses many of the problems associated with prior art flat-panel display technologies, it nevertheless suffers from several shortcomings and drawbacks which have made widespread commercial applications thereof hitherto impractical.
In particular, within Applicants' prior art flat panel display system design, the laser light beams sustain very high intensity losses during beam steering and transmission operations, making it very difficult to produce bright images without using high power laser light sources. In addition, within Applicants' prior art flat panel display system design, numerous laser light sources are required, rendering the cost of manufacture prohibitive.
Thus, there is a great need in the art for an improved method and apparatus for steering electromagnetic beams within substantially planar display structures in order to produce color images therefrom, while avoiding the shortcomings and drawbacks of prior art apparatus and methodologies.